1. Field of the Invention
The present invention relates to an input buffer circuit of a synchronous semiconductor memory device, and more particularly to an input buffer circuit of the semiconductor memory device capable of reducing the current flowing into the input buffer circuit in a self-refresh mode.
2. Description of Related Art
A differential amplifier type input buffer has been used as the input buffer of synchronous semiconductor memory devices such as a Double Data Rate Synchronous Dynamic Random Access Memory (DDR SDRAM). When the synchronous semiconductor memory device is in the on state, the current flowing into the differential amplifier type input buffer is more than 200 μA. When the synchronous semiconductor memory device is in the self-refresh mode, the total current of the DDR SDRAM is about 2 mA. As a result, the current flowing into the input buffer in the self-refresh mode takes a large portion of the total current of DDR SRAM.
A conventional synchronous semiconductor memory device used the differential amplifier type input buffer in the self-refresh mode as in the normal mode. Therefore, the power consumption of the device was large.